Virtual reality (VR) is an immersive environment which is created by a computer and with which users have real-time, multisensorial interactions. Typically, these interactions involve some or all of the human senses through either visual feedback, sound, force and tactile feedback (i.e. reflection), smell and even taste. The key to immersive realism is the capacity of the user to use his/her hand to interactively manipulate virtual objects. Unfortunately, the majority of existing commercial virtual reality systems use hand-sensing devices that provide no haptic feedback. Nevertheless, some efforts have been made to provide means for presenting force and tactile information to the user's hand. By force information, it is meant the application of a set force to a selected part of the hand, for example, a finger. By tactile information, it is meant the application of a stimuli, e.g., a vibration, to a selected part of the hand, e.g., a fingertip pad. This stimulus, could simulate surface texture or dynamic conditions at the contact, for example. A few examples of existing force reflecting devices are the EXOS SAFiRE™, the Master II Hand Master device at Rutgers university, the PERCRO Force-Reflecting Hand Master and the Sarcos TOPS Force-Reflecting Hand Master. Some tactile feedback devices that have been developed include the PERCRO Position-Sensing and Tactile Feedback Hand Master and the EXOS TouchMaster™.
Virtual reality is not the only field where it is desirable to feed back force and tactile information to a human user/operator. Another common area is telerobotics. Some of the devices mentioned above are also often used as telerobotics interfaces. Some examples in the literature of feedback devices designed more specifically for telerobotics include the tactile shape sensing and display system developed by Kontarinis et al., the voice-coil based tactile feedback device used by Patrick et al. and the pin-based tactile display array developed by Kaczmarek and Bach-y-rita. Other applications for a vibrotactile unit include, but are not limited to, gesture recognition, music generation, entertainment and medical applications.
In an ideal case, it would be desirable to provide full force and tactile feedback to a user to make the virtual reality or telerobotic experience as realistic as possible. Unfortunately, most force feedback devices are cumbersome, heavy, expensive and difficult to put on and remove. Many of the tactile feedback solutions are also cumbersome, complex and fragile. Additionally, some of the tactile feedback devices described in the literature, such as small voice coils mounted to directly contact the skin, tend to numb the skin after only a few seconds of operation and then become ineffective as feedback devices.